Solar water splitting is being investigated in the search for a production method of clean renewable fuels. However, the vast majority of the water splitting photo-electrochemical cells cannot drive the water splitting reaction without the assistance of an external power source. In order to provide the photo-electrochemical cell (PEC) the added power, the cells are usually connected to photovoltaic devices in a tandem arrangement or as external power sources.
These two methods suffer from severe disadvantages, however. In the tandem arrangement, the PEC is connected in series to a photo-voltaic (PV) cell. As a result, the current through the system is determined by the PEC current, which is significantly lower than the maximum power point current of the PV cell. As a result, the operating point of the PV cell is far from optimal and the overall system efficiency is very low. When a PV cell is connected to a PEC through a DC-DC converter (e.g., as an external power source), the operating point of each subsystem can be chosen independently. However, since the PV cell must be decoupled from the PEC, this comes at the price of a significant increase in the system magnitude and additional losses inflicted by the DC-DC conversion.